Test flow rejected
At their meeting last month, the Glen Canyon Adaptive Management Working Group rejected a proposal to conduct a high-flow, beach-building release from the dam in the spring.
The proposed experimental flood for sediment redistribution in Grand Canyon during March was rejected after consideration by the group. The AWG's purpose is to balance competing interests of power, recreation and environmental concerns in the management of Glen Canyon Dam's water releases to protect and enhance the natural resources of Grand Canyon National Park.
According to researchers at the Grand Canyon Monitoring and Research Center, severe rainstorms last fall placed an estimated 1.5 to 2.6 million tons of fine sediments into the Colorado River below the dam. The planned 42,000 cfs (cubic feet per second) flow was intended to transfer that sand and redistribute it in the canyon and along the riverbanks.
Since Glen Canyon Dam began operating in 1963, the natural sediment flow has been trapped behind the dam with the effects felt downriver. The natural deposition of sandbars in the river's eddies provided nursery habitat for spawning fish, now endangered. Additionally, wind blown beach sand enhanced dunes that can help protect cultural sites from degradation by natural erosion. Proponents of the flood hoped that it would mimic these natural processes.
The Center predicts that most of the existing sand in the Grand Canyon will eventually be transported and deposited into Lake Mead, the reservoir downstream of Grand Canyon.
Since some of the flow in a simulated flood comes from the dam's bypass tubes that do not spin generators to make electricity, the majority of AMWG representatives felt that the experimental flow would decrease hydropower revenues.
Other working group members felt that the high flows would harm the non-native trout populations and the aquatic food web.
Also, the short time frame for adequate planning and obtaining required environmental clearances caused concern within the group. Scheduled generator maintenance at the dam prevents an experimental flood after March.
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